Afaik you dont need all that stuff if you only want to use your PC.
Here it would be sufficient to have a RPi where you can connect your LED's (with the right LED's you dont even need an Arduino) which runs Hyperion and the Windows Grabber. Both systems would be connected by LAN.
More experienced Member should correct me if i am wrong.
Infact i plan nearly the same because my HTPC runs Kodi and my Game PC Windows. These are the only two sources which feed my TV. So i dont see any need for using USB Grabber, HDMI Splitter etc.